(a) Technical Field
The present invention relates to a fuel cell separator with a gasket. More particularly, it relates to a fuel cell separator with a gasket and a method for manufacturing the same, which can prevent corrosion of the separator and improve corrosion resistance of the separator.
(b) Background Art
Referring to FIG. 5, which shows the configuration of a fuel cell stack based on a unit cell, a membrane electrode assembly (MEA) is located in the middle of the fuel cell stack and includes a polymer electrolyte membrane 10 and an electrode/catalyst layer such as an air electrode (cathode) 12 and a fuel electrode (anode) 14 disposed on each of both sides of the polymer electrolyte membrane 10. Hydrogen ions (protons) are transported through the polymer electrolyte membrane 10, and an electrochemical reaction between hydrogen and oxygen takes place in the electrode/catalyst layer.
A gas diffusion layer (GDL) 16 and a gasket 18 are sequentially stacked on both sides of the MEA, where the cathode 12 and the anode 14 are located. A separator 20 including flow fields for supplying fuel and discharging water generated by the reaction is located on the outside of the GDL 16, and an end plate 30 for supporting and fixing the above-described components is connected to each of both ends thereof.
At the anode 14 of the fuel cell stack, hydrogen is dissociated into hydrogen ions (protons, H+) and electrons (e−) by an oxidation reaction of hydrogen. The hydrogen ions and electrons are transmitted to the cathode 12 through the electrolyte membrane 10 and the separator 20, respectively. At the cathode 12, water is produced by an electrochemical reaction in which the hydrogen ions and electrons transmitted from the anode 14 and the oxygen in air participate and, at the same time, electrical energy is produced by the flow of electrons.
The separator 20 (for example, a metal separator) of the fuel cell stack functions as follows.
The separator 20 acts as a path for supplying a reducing gas and an oxidizing gas to the cells, a path for supplying coolant for cooling the fuel cell stack, and a path for transmitting the generated current. Thus, the separator 20 should be air-tight and liquid-tight such that the reducing gas, the oxidizing gas, and the coolant are not mixed together. Therefore, a rubber sealing material can be applied to the surface of the separator 20 to maintain the air-tightness and liquid-tightness and, at the same time, serve to maintain the load.
Moreover, the gasket 18 of the fuel cell stack is bonded to the separator 20 to define each of the unit cells of the fuel cell stack and to serve to seal the hydrogen, coolant, and air flow fields, respectively, formed on the surface of the separator 20. Therefore, for smooth functioning of the gasket 18, the method of bonding the gasket 18 to the separator 20 and the selection of a gasket base material should be carefully considered during manufacturing of the fuel cell stack.
A conventional method of integrally bonding a gasket 18 to a separator 20 in consideration of these factors will be described with reference to FIGS. 3 and 4 below.
First, as shown in FIG. 3, an adhesive is coated on a portion of the surface of a metal separator 20 (hereinafter referred to as a separator), on which a gasket 18 is injection molded, and the edges of the separator 20 are fixed by the pressure of an injection mold 40. Then, a gasket base material is injected into the injection mold 40 and, at the same time, the injection mold 40 applies a pressure to the gasket 18 to be integrally molded on the surface of the separator 20.
Referring to FIG. 4 showing the structure of the separator on which the gasket is integrally molded, the gasket 18 is not formed on the edges of the separator 20, and thus the surface of the edges of the separator 20, on which the gasket 18 is not formed, is always exposed to the outside.
The reason that the gasket is not formed on the edges of the separator is that the edges of the separator are in close contact with the injection mold and clamped by the injection mold when the gasket is integrally molded on the separator.
While the gasket is not formed on the edges of the separator, this does not have a significant effect on the air-tightness performance. However, as the edges of the separator are always exposed to corrosive environments in the cells of the fuel cell stack, corrosion occurs over time, which results in a reduction in durability of the separator.
Moreover, in the case where there is a slight difference in thickness in the longitudinal direction of the edges of the separator, the force of the injection mold including upper and lower mold to clamp the edges of the separator is not uniformly applied, which results in the formation of burrs on the surface of the gasket. Therefore, a finishing process for removing the burrs is required, which reduces the efficiency of the injection molding process.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.